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Near-ultraviolet imaging of Jupiter's satellite Io with the Hubble Space Telescope
Boksenberg, A.; Barbieri, C.; Sartoretti, P. +7 more
The surface of Jupiter's Galilean satellite Io has been resolved for the first time in the near ultraviolet at 2850 A by the Faint Object Camera (FOC) on the Hubble Space Telescope (HST). The restored images reveal significant surface structure down to the resolution limit of the optical system corresponding to approximately 250 km at the sub-eart…
Observation of non-drifting radio emissions associated with the intense solar activity in March 1991
Stone, R. G.; Fainberg, J.; Reiner, M. J.
Three very unusual radio bursts, separated in time by 4 hours and 35 minute-intervals were observed on March 28, 1991 by the radio and plasma wave (URAP) experiment on the Ulysses spacecraft. Although they are preceded by drifting type III bursts at high frequencies, they show no frequency drift at frequencies from 52 kHz down to 16 kHz. In additi…
A Search for Weak Ultraviolet Interstellar Absorption Features in IUE Spectra of rho Ophiuchi and zeta Ophiuchi
York, D. G.; Welty, D. E.; Hobbs, L. M. +1 more
We have applied procedures designed to reduce substantially the non-random, so-called "fixed-pattern" noise present in IUE spectra to archival long-wavelength light-dispersion spectra of rho Ophiuchi and zeta Ophiuchi. Substantial elimination of the fixed-pattern noise via flat fielding can yield 2-sigma equivalent width limits of 5-10 mA from the…
Unusual radio and plasma wave phenomena observed in March 1991
Stone, R. G.; Fainberg, J.; Reiner, M. J.
During the intense solar flare activity in March 1991 a number of unusual radio emission and Langmuir wave phenomena were observed by the radio and plasma wave (URAP) experiment on the Ulysses spacecraft. These phenomena were associated with unusual conditions in the interplanetary medium (IPM) presumably resulting from intense solar activity. Som…
The energy distribution of 21 Comae Berenices (A3p): comparison to standard stars of similar spectral types and modeling.
Monier, R.; Megessier, C.
The energy distribution (ED) of 21 Com is constructed from 1200 to 22000 Å using UV and optical spectrophotometry and recent IR photometry (Fernley 1990). The comparison of the ED with those of standard A3 stars confirms the A3 spectral type ascribed to 21 Com by Cowley et al. (1969) and reveals many similarities with the A3 IV standard τ Vir. The…
A Minor Outburst during the Quiescent Period of the Symbiotic Star Ch-Cygni
Hack, Margherita; Aydin, Cemal
We have studied a few optical spectra of the symbiotic star CH Cygni obtained in the period January 1990-June 1991, which indicate that a mild increase of activity occurred between July and December 1990. This increase of activity is confirmed by the IUE observations made in the same period. In fact, in this period of time, we have observed an inc…
Possible detection of Lyman alpha emission in the A7 III star gamma Bootis
Freire Ferrero, R.; Catalano, S.; Gouttebroze, P. +1 more
We analyze the archive high dispersion IUE spectrum SWP 10885 of Gamma Boo (A7 III) in the Ly-alpha region, using our own software. A faint stellar emission overlayed by a saturated interstellar absorption is detected. This result and the previous detection of Ly-alpha emission in Altair and Alpha Cep do suggest that the presence of chromospheric …
The radial velocity and binary of X Persei.
Stickland, D. J.
It is shown on the basis of radial velocity measurements on high-resolution spectra of X Persei from the IUE archive that there is no variation above the level of a few km/s and thus no need for a massive unseen component in the system. This does not rule out a neutron star or white dwarf orbiting in the variable wind of the Be star.
TYCHO Astrometry Calibration
Pedersen, H.; Lindegren, L.; Bastian, U. +6 more
The Hipparcos satellite's star mapper gives photon counts in two spectral channels simultaneously. The transit times and the signal amplitudes for each star across two groups of four slits are derived and used for astrometry and photometry, respectively, and this constitutes the Tycho project. The present paper describes the Tycho astrometric data…
First X-ray spectrum of the most luminous quasar PKS 2126-158.
Ghosh, K. K.; Soundararajaperumal, S.
For the first time the detailed results of the spectral analysis of the X-ray (0.1-10 keV) spectrum of the luminous (z = 3.27), radio-loud quasar, PKS 2126 - 158, are presented. The spectrum of this quasar was obtained from the EXOSAT database. Power law and fixed absorption model fits well with the spectrum. The parameters of this model suggest t…